What to do:
Take lamb rack out of the fridge up to 2 hrs before cooking it. If you have less time it's fine... it's just optimal to not shock the fridge cold meat before searing it - it will work though if you don't have time.
Preheat oven to 450°F.
Wash and stick a fork into 3-4 russet potatoes - put them in the heating up oven and forget about them until later.
** Place the asparagus in an oven-proof dish and sprinkle with sea salt and a generous amount of olive oil – turn to coat. Shell the peas and cut green beans into 1” pieces – set aside. (if using frozen peas they are ready to cook at this point – no need to thaw them)
About 40 minutes before you want to eat, dry the rack with paper towels if it looks wet. Rub the lamb over all with your combined salt and pepper mix (don't feel you have to add anything else other than salt and pepper).
Find an oven-proof sauté pan big enough for the lamb and small enough that you can get the asparagus in alongside it. The sauté pan needs to have a little bit of side on it, as you will be adding liquid before you put it in the oven
Place into this pan a tbsp of Olive Oil over high heat on your stovetop. When oil is hot but not smoking, add the rack and sear it (till it turns golden on all sides). About 5 minutes total.
Turn off the heat and dump the cognac over the top of the rack. There will be lots of white smoke - be careful if using gas that you don't have a burner turned on when you do this or you will have fire with the smoke (which works to burn off the alcohol but I'm still not comfortable with it - try at your own peril). In about 1-2 minutes the smoke will clear and the liquid will reduce by itself because of the heat of the pan. If you have burned bits stuck in the pan feel free to scrape them around and into the sauce at this point.
Then put the pan in the oven. Put the prepared asparagus dish into the oven as well.
Check the potatoes - they will have an internal temperature of 200F when they are done, or you can stick a fork in them to see if they are cooked through.
*** Meanwhile in a medium frying pan heat a tbsp of butter and ½ tbsp of Olive Oil over medium heat. Add the beans and the peas stirring well and when they start to get bright green turn off the heat and let them finishing cooking with the residual heat (if you are using frozen peas you want to wait until the beans are just starting to turn color then add the peas and cook for 1-2 mins more and turn the heat off.)
The lamb needs 20-30 minutes depending on how big your rack was. You want to take it out when the internal temp of the center of the rack reads about 125F for medium rare (120F for rare). The temperature will raise about 5 degrees after you remove the rack. Most of the time I forget and it makes it to about 130 before I remove it from the oven. That's okay. It will still be medium rare - just a bit further towards the medium. The asparagus is done when starts to get slightly pliable and get a nice golden cast to it.
Let it rest 5-10 minutes before carving it - if your family can wait that long. It really does make a difference.